Electric heating – Metal heating – By arc
Reexamination Certificate
1999-10-22
2001-10-23
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
By arc
C219S130010
Reexamination Certificate
active
06307177
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a process for determining the working voltage on a welding device with a controllable current source and to the welding device wherein the process uses a controllable welding cur-rent source, wire electrode wire feed means and a device for determining the working voltage on a welding current source.
BACKGROUND OF THE INVENTION
The reference J. Latimer, Automatic Welding, deals with the control of the arc length during submerged arc welding. A constant-current power source with usually larger wire diameters is used here, and slight changes in the amount of arc and thus in the arc voltage cause only a slight change in the current intensity. The arc length, which may change because of different effects, can be controlled by changing the electrode feed speed. The voltage is tapped for this purpose from the terminals of the current source or from the contact tube. The electrode feed speed is reduced when the arc length decreases and a corresponding voltage drop occurs, and, conversely, it is increased as the arc length increases. The welding current source is designed as a constant-current power source and is not controlled. U.S. Pat. No. 3,054,885 shows a system for monitoring a plurality of welding units by one operator. In the case of disturbance in one unit, this unit switches itself off and signals the failure to the monitoring operator, who is then to eliminate the disturbance. The monitoring is performed via various relays.
SUMMARY AND OBJECTS OF THE INVENTION
The primary object of the present invention is to determine the actual value of the working voltage better and more accurately.
According to the invention, a process is provided for determining the working voltage on a welding device with a controllable welding current source, a wire electrode, a wire feed means and a device for determining the working voltage on the welding current source. The measured working voltage is used to control the welding current source. The working voltage is determined at least partially outside the output terminals of the welding current source. One tap is provided at a spaced location before a point at which the current is introduced and directly on the wire electrode or on the wire feed roller of the wire electrode.
According to another aspect of the invention a device is provided with a welding current source, a wire electrode, a wire feed and the device for determining the working voltage on the welding current source. The welding current source has a controller and an output part. The taps are located at least partly outside the output terminals of the welding current source and are connected to the controller of the welding current source. One tap is arranged at a spaced location before a point at which the current is introduced and directly on the wire electrode or on the wire feed roller of the wire electrode.
The present invention offers the advantage that the measured voltage determined can be reduced essentially to the sum of the partial voltage drops over the arc and over the free end of the wire electrode, through which the welding current flows, wherein the partial voltage drops are relevant for the welding process proper and wherein the sum is necessary for the control of the welding current source. The voltage drop over the resistance of the wire electrode between one tap and the point at which the current is introduced is insignificant, because the measured current flowing over it is very low. Thus, essentially only the voltage drops over the useful resistances are used for controlling the welding current. The control is correspondingly accurate. Disturbance variables, which adversely affect the control and consequently the extrapolability, the comparability, the reproducibility, the process stability, and ultimately the quality of the weldings, are ruled out.
Due to the fact that the voltage over the useful resistances proper, the free end of a wire electrode and the arc can be controlled highly accurately in this manner, a constant welding process is obtained despite changing partial resistances in the welding circuit. Thus, even though the wear of the contact tube and welding lines with increasing temperature do cause increased partial resistances in the welding circuit, these do not affect the above-mentioned voltage drop over the useful resistances and consequently not the resulting arc length either.
Furthermore, the characteristic provided by the current source with the defined gradient is present on these useful resistances, and this characteristic is also available on the arc with slight deviations because of the small value of the partial resistances and consequently of the partial voltage drops over the free end of a wire electrode and the workpiece compared with the arc.
The reproducibility and the extrapolability are ensured, at least as far as the voltage is concerned, to a high extent with this method. This means that voltage values from data banks that were set up with this method of determining the actual value of the voltage can be applied to welding units without preliminary adjustment and they lead largely to the same welding result. Since the “drift of the welding parameters,” especially concerning the voltage drop over the useful resistances and consequently above all the arc length, is more or less ruled out, the quality of the weldings meets the required criteria over longer periods of time than before. The intervals between changing the contact tubes can foreseeably also be considerably prolonged.
The invention may also use of existing taps on the workpiece or on the output terminal of the welding current source for the workpiece line or in the welding current source or on the workpiece. Furthermore, the intention provides for the possibilities of utilizing existing feed means and connection systems for torch hose bundles.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.
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Hitachi Seiko K. K., Apr. 8, 1985, Power Source for Arc Welding,Patent Abstracts of Japan, Aug. 15, 1985, vol. 9/No. 1985.
Kuka Schweissanlagen GmbH
McGlew and Tuttle , P.C.
Shaw Clifford C.
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